Fumaric acid esters (FAE; fumarate esters, e.g., alkyl or dialkyl fumarate esters such as dimethyl fumarate or monomethyl fumarate) are pharmacologically active substances used for treating hyperproliferative, inflammatory, or autoimmune disorders. They were first used to treat psoriasis and were licensed for this indication in Germany in 1995 as Fumaderm® (Biogen Idec, Inc., Cambridge, Mass., USA). Fumaderm® produces various undesirable side effects, including flushing, headaches, dizziness, eructation, nausea, vomiting, abdominal and intestinal cramps, and diarrhea. High concentrations of the drug released in the stomach are believed to be responsible for such side effects.
After oral intake, the main component of Fumaderm®, dimethyl fumarate (DMF), is hydrolysed by esterases to monomethyl fumarate (MMF), the bioactive metabolite. After absorption in the small intestine, MMF is believed to interact with immunocytes in the bloodstream. The primary plasma metabolites of DMF are monomethyl fumarate, fumaric acid, citric acid, and glucose. Monomethyl fumarate is further metabolized in the tricarboxylic acid cycle to carbon dioxide and water.
An oral formulation of DMF was developed and approved for the treatment of multiple sclerosis. This formulation, TECFIDERA® (Biogen Idec, Inc.), is available as hard gelatin delayed-release capsules containing 120 mg or 240 mg of granulated dimethyl fumarate enterically coated minitablets. See International Patent Application Publication No. WO 2013/119677 and U.S. Pat. No. 6,509,376. TECFIDERA® was intended to reduce the undesirable side effects by preventing release of DMF in the stomach.
The enterically coated DMF granules in TECFIDERA®, however, lack uniformity in shape and size, and the enteric coating may not be evenly distributed over the minitablets. This lack of homogeneity can diminish the enteric properties and affect the acid-resistance, dissolution, and release rates. In addition, the integrity of the acid-resistant coating fails when the coating cracks or flakes off. This leads to DMF release in the stomach and can cause flushing and the negative gastrointestinal side effects.
A subject's stomach content also affects delivery of DMF from TECFIDERA®. A meal was shown to decrease Cmax by 40% and delay Tmax from 2.0 hours to 5.5 hours; the AUC was unaffected. See WO 2006/037342. A reduction in the incidence of flushing by approximately 25% in the postprandial state was also observed. See TECFIDERA® Prescribing Information 03/2013 (Biogen Idec Inc.).
DMF sublimes at relatively low temperatures. About 15-20% of the DMF active ingredient is lost owing to sublimation during the wet-granulation processing used to manufacture TECFIDERA®. See WO 2013/076216. Sublimation also causes loss of DMF during storage and unused TECFIDERA® capsules must be discarded 90 days after a bottle of the capsules is opened. Accordingly, it is desirable to develop oral controlled release formulations of fumarate esters that: (1) provide enhanced bioavailability of the fumarate esters as compared to TECFIDERA® or other solid dosage forms comprising granulated forms or minitablets; (2) prevent flushing and the undesirable GI side effects associated with oral administration of fumarate esters; (3) reduce or eliminate fumarate ester sublimation during manufacturing and storage; (4) increase the long-term stability of the pharmaceutical composition; and (5) provide a variety of different release profiles, dose strengths, dosage forms, and dosing regimens.